Type 1 diabetes mellitus is caused by the autoimmune destruction of pancreatic beta cells. Thus, efforts in recent years have centered on the development of approaches to slow or prevent the destruction of the endogenous beta cells, provide them from an exogenous source by transplantation, or induce their de novo regeneration. The current proposal focuses on the first two of these directions. The overall long-term goals of this program are 1) to identify key components in the autoimmune response to beta cells and design new therapeutic approaches for the protection and preservation of endogenous beta cells, and 2) to develop genetically engineered human beta-cell lines and human islets to replace damaged or non-functional beta cells. These goals are addressed by projects. In Project 1, synthetic and natural peptide ligands will be identified for beta cell-cytotoxic T cells restricted to the human class I MHC molecule HLA-A2. The disease relevance of these ligands will be examined in NOD mice transgenically expressing HLA-A2 using peptide/MHC tetramer and tolerization studies. Findings will be translated to humans by testing the hypothesis that HLA-A2-positive type 1 diabetes patients will exhibit overlapping T cell reactivities to those seen in NOD.HLA-A2.1 mice. In Project 2, the mechanisms by which Adenoviral E3 gene products protect islets from allogeneic rejection and autoimmune destruction will be examined using murine and human islets and beta-cell lines, including conditionally transformed murine cells and the human cells produced in Project 3. In Project 3, human hepatic progenitor cells will be engineered to become surrogate beta-cells having the capacity to store and secrete insulin physiologically, thus serving as an alternative to human islets as a source of transplantable beta-cells.